Method for sending packet data, base station, and mobile station

ABSTRACT

A method for sending packet data is provided, which includes the following steps. Packet data from a source mobile station (MS) is received. The packet data includes an identity of a destination MS. A routing cache table is searched for a path to the destination MS. An interface is selected if the path to the destination MS is found. The packet data is forwarded through the selected interface according to the found path. Other two methods for sending packet data corresponding to the method for sending packet data as well as an MS and a base station (BS) corresponding to the method for sending packet data are provided. Therefore, link processing can be performed at the MS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/855,169, filed on Aug. 12, 2010, which a continuation ofInternational Application No. PCT/CN2009/071847, filed on May 19, 2009,The afore-mentioned patent applications are hereby incorporated byreference in their entireties.

FIELD OF THE TECHNOLOGY

The present invention relates to the filed of communications technology,and more particularly to a method for sending packet data, a basestation (BS), and a mobile station (MS).

BACKGROUND OF THE INVENTION

A multi-hop relay is a measure executed when a network has no fixedaccess points, which is first researched and applied in an adhocnetwork. An adhoc network has no fixed infrastructure and no fixedrouters, in which all nodes are mobile and all the nodes can keepcontact with other nodes in a random mode dynamically. All nodes areequal in the network, and no central control node needs to be set. Thenode in the network not only has functions needed by an ordinary mobilestation (MS), but also has a packet forwarding capability. In such anenvironment, due to the limitation of wireless coverage of the MS, twouser MSs that are incapable of direct communication can perform packetforwarding through other nodes, which is referred to as multi-hopcommunication. In recent years, the multi-hop relay technology isapplied in the conventional cell network, and the establishment of anew-type cell multi-hop network also becomes a new research focus in thewireless communication. In a cell multi-hop network, an MS can beconnected to a corresponding cell base station (BS) through one or morerelay nodes. The use of the relay nodes decreases a path loss andimproves communication quality of each transmission link, so thatcapacity and coverage of the entire cell of origin are greatlyincreased. In the cell multi-hop network, it is very important forperformance improvement of the entire system to find suitable relaynodes, and therefore an effective routing algorithm is required.

A method for sending packet data in the prior art is described asfollows. In consideration of a feature that a cell multi-hop network iscentered on the BS, a conventional distributed routing mode is changedinto a centralized processing mode that the BS provides routing for eachnode in a unified mode. The BS maintains statuses of links among allMSs, and selects paths for communication of the MSs in a centralizedmode according to the maintained link statuses. Through the centralizedprocessing mode, the BS can gradually obtain a topological structure ofthe cell by processing and maintaining information acquired in therouting process.

In addition, in consideration of a two-hop access cell, when a relay isneeded as the quality of a link between the MS and the BS isdeteriorating, a relay request is first sent to the BS to require the BSto provide a multi-hop routing. If the BS cannot find the path, the MSbroadcasts a relay-request routing signal to nearby nodes. Afterreceiving the relay request, an intermediate node returns a signaling tothe BS. Therefore, the BS can obtain quality of a first-hop link andmeasure quality of a second-hop link. Thus, every time a relay requestresponse sent by an intermediate node is received, the BS updates itsown channel quality matrix once. After the channel quality matrix iscompletely updated, the BS executes the routing algorithm again. At thistime, the BS has obtained all channel information related to the MS, sothat a relay node is selected and the selected relay node is returned tothe MS as a feedback, so as to enable the MS to send packet data throughthe relay node.

During the research of the prior art, the inventor finds that by usingthe method for sending packet data in the prior art, a relay requestneeds to be sent for packet relay distribution each time and the BSperform all the link processing, This results large resource overhead ofthe BS and high communication complexity.

SUMMARY OF THE INVENTION

The present invention embodiment is directed to a method for sendingpacket data, a base station (BS), and a mobile station (MS), so as toperform link processing at the MS.

The present invention provides a method for sending packet data, whichincludes the following steps.

Packet data from a source MS is received. The packet data includes anidentity of a destination MS.

A routing cache table is searched for a path to the destination MS.

An interface is selected if the path to the destination MS is found.

The packet data is forwarded through the selected interface according tothe found path.

The present invention further provides a method for sending packet data,which includes the following steps.

Packet data that needs to be sent is obtained.

It is determined whether an access status is direct access.

If the access status is direct access, the packet data is sent to a BS.

If the access status is not direct access, a cluster head is selectedfrom a cluster head table, and the packet data is sent to the clusterhead.

The present invention further provides a method for sending packet data,which includes the following steps.

Packet data is received. The packet data includes an identity of adestination MS.

An MS status table is searched for the identity of the destination MS.

If the identity of the destination MS is not found, the packet data issent to a core network.

If the identity of the destination MS is found, it is determined whetheran access status of the destination MS is direct access.

If the access status of the destination MS is direct access, the packetdata is sent to the destination MS. If the access status of thedestination MS is not direct access, a cluster head is selected, and thepacket data is sent to the selected cluster head.

The present invention further provides an MS, which includes a receivingunit, a searching unit, a selecting unit, and a sending unit.

The receiving unit is adapted to receive packet data from a source MS.The packet data includes an identity of a destination MS.

The searching unit is adapted to search a path to the destination MS ina routing cache table according to the identity of the destination MSreceived by the receiving unit.

The selecting unit is adapted to select an interface when the path tothe destination MS is found by the searching unit.

The sending unit is adapted to forward the packet data through theinterface selected by the selecting unit according to the path to thedestination MS found by the searching unit.

The present invention further provides another MS, which includes anobtaining unit, a determining unit, a selecting unit, and a sendingunit.

The obtaining unit is adapted to obtain packet data that needs to besent.

The determining unit is adapted to determine whether an access status ofthe MS is direct access.

The selecting unit is adapted to select a cluster head from a clusterhead table when the determining unit determines that the access statusof the MS is not direct access.

The sending unit is adapted to send the packet data to a BS when thedetermining unit determines that the access status of the MS is directaccess; and send the packet data to the cluster head selected by theselecting unit when the determining unit determines that the accessstatus of the MS is not direct access.

The present invention further provides a BS, which includes a receivingunit, a searching unit, a determining unit, a selecting unit, aselecting unit, and a sending unit.

The receiving unit is adapted to receive packet data. The packet dataincludes an identity of a destination MS.

The searching unit is adapted to search the identity of the destinationMS in an MS status table.

The determining unit is adapted to determine whether an access status ofthe destination MS is direct access when the searching unit finds theidentity of the destination MS.

The selecting unit is adapted to select a cluster head when thedetermining unit determines that the access status of the destination MSis not direct access.

The sending unit is adapted to send the packet data to a core networkwhen the searching unit does not find the identity of the destinationMS; send the packet data to the destination MS when the determining unitdetermines that the access status of the destination MS is directaccess; and send the packet data to the cluster head selected by theselecting unit when the access status of the destination MS is notdirect access.

As can be seen from the technical solutions in the embodiments of thepresent invention, because the MS in the embodiments can determine amode of sending the packet data according to its own access status andthe cluster head table is maintained in the MS, only a cluster headneeds to be selected from the cluster head table when the packet data issent and then the packet data is sent to the cluster head or directlysent to the BS. As long as information of the cluster head exists in thecluster head table, the MS does not need to send a relay request to theBS when the packet data is sent, that is, the link processing isperformed at the MS, so that resource overhead of the BS is decreasedand the MS only needs to maintain the information of the cluster head,thereby reducing the communication complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the technical solution according to the embodiments of thepresent invention or in the prior art more clearly, the accompanyingdrawings for describing the embodiments or the prior art are providedbriefly below. Apparently, the accompanying drawings in the followingdescription are only some embodiments of the present invention, andpersons of ordinary skill in the art can derive other drawings from theaccompanying drawings without creative efforts.

FIG. 1 is an architectural view of a cell adhoc network according to anembodiment of the present invention;

FIG. 2 is a flow chart of a method for sending packet data according toa first embodiment of the present invention;

FIG. 3 is a flow chart of a method for sending packet data according toa second embodiment of the present invention;

FIG. 4 is a flow chart of a method for sending packet data according toa third embodiment of the present invention;

FIG. 5 is a flow chart of a method for sending packet data according toa fourth embodiment of the present invention;

FIG. 6 is a flow chart of a method for sending packet data according toa fifth embodiment of the present invention;

FIG. 7 is a structural view of an MS according to a first embodiment ofthe present invention;

FIG. 8 is a structural view of an MS according to a second embodiment ofthe present invention;

FIG. 9 is a structural view of an MS according to a third embodiment ofthe present invention;

FIG. 10 is a structural view of an MS according to a fourth embodimentof the present invention;

FIG. 11 is a structural view of a BS according to a first embodiment ofthe present invention; and

FIG. 12 is a structural view of a BS according to a second embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description is directed to the technical solutionof the present invention with reference to the accompanying drawings.However, the embodiments to be described are only part of, rather thanall of, the embodiments of the present invention. All other embodiments,which can be derived by those skilled in the art from the embodimentsgiven herein without any creative efforts, fall within the scope of thepresent invention.

A cell adhoc network related to the embodiment of the present inventionis first introduced. Architecture of the cell adhoc network provided inthe embodiments of the present invention is shown in FIG. 1.

Different sector clusters inside the cell form an intra-cell virtualcluster 1011. The cluster heads in the intra-cell virtual clusterperform inter-sector cooperation, so that a mobile station (MS) canaccess flexibly.

The sector clusters in adjacent cells form an inter-cell virtual cluster1021. The cluster heads of the inter-cell virtual cluster performinter-cell cooperation, so as to facilitate inter-cluster communicationand inter-cell load balance during hybrid access and cooperative access.

The intra-cell virtual cluster is divided into hybrid access zones 1012,cluster head zones 1013, and direct access zones 1014 according to adistance away from a base station (BS). A hybrid access zone is thefarthest away from the BS and a direct access zone is the nearest to theBS. If an MS is located in a direct access zone and a cluster head zone,an access status of the MS can be direct access. If the MS is located inthe hybrid access zone, the MS can access the BS through cell relay andat this time the access status of the MS can be cooperative access.Alternatively, the MS can access the BS through adhoc relay and at thistime the access status of the MS can be hybrid access. If the MS isunable to receive information of the BS and the cluster head, the accessstatus of the MS is “adhoc”. The access statuses of the MS in differentaccess zones are shown in Table 1.

TABLE 1 Communication Mode Access Zone MS Access Status Description Cellaccess Direct access zone, Direct access Direct access to the BS (directaccess cluster head zone S = 00 and hybrid Hybrid access zoneCooperative Access to the BS through cell access to the access relay BS)S = 01 Hybrid access zone Hybrid access Access to the BS through S = 11adhoc relay Adhoc access Direct access zone, Adhoc Adhoc access (noaccess to Hybrid access zone, S = 10 the BS) Cluster head zone

The inter-cell virtual cluster is divided into hybrid access zones 1022,cluster head zones 1023, and direct access zones 1024 according to adistance away from a center of the inter-cell virtual cluster. A hybridaccess zone is the farthest away from the center of the inter-cellvirtual cluster and a direct access zone is the nearest to the center ofthe inter-cell virtual cluster.

In order to realize the operability and manageability of the MS adhocmode, the selection and clustering of the cluster heads in theembodiments of the present invention are initiated by the BS. Theselection and clustering of the cluster heads can be performedperiodically or when triggered by an event, for example, after the BSreceives a relay request sent by the MS. In an embodiment of the presentinvention, the selection and clustering of the cluster heads can beperformed according to the following process.

The BS broadcasts a cluster-head selection request within the coverageof the local cell. The cluster-head selection request carries parameterssuch as location information of the BS, a cell radius R, a cellutilization U, and a cluster-head threshold value C. The MS thatreceives the cluster-head selection request calculates a distance Lbetween the MS itself and the BS. If the L is greater than a thresholdvalue 1 (in an embodiment of the present invention, the threshold value1 can be R/2) and smaller than a threshold value 2 (in an embodiment ofthe present invention, the threshold value 2 can be 3R/4), it indicatesthat the MS is located in the cluster head zone and the MS sets theaccess status S as direct access. Otherwise, it indicates that the MS islocated in the direct access zone or the hybrid access zone, and at thistime the access status S of the MS can be first set as direct access andsubsequently the access status S is updated by the MS according to acluster head advertisement.

The MS located in the cluster head zone estimates quality of a linkbetween the MS itself and the BS according to information of thecluster-head selection request. The quality of the link between the MSand the BS can be a path loss P_(Loss). The MS then determines whetherthe requirement of the cluster head selection is satisfied according toits own rest energy information N_(Rest). In an embodiment of thepresent invention, if P_(Loss)/N_(Rest)<C for an MS, it indicates thatthe MS satisfies the requirement of the cluster head selection, andtherefore the MS sends a cluster head advertisement. Information of thecluster head advertisement includes resource information of the MS andutilization U of the cell in which the MS is located. The resourceinformation of the MS includes rest energy of the MS and a path lossbetween the MS and the BS. The sent cluster head advertisement can be acell cluster head advertisement and adhoc cluster head advertisement.

The MS that receives the cluster head advertisement updates the accessstatus and the cluster head table.

If a default access status S of the MS is “adhoc”, the MS that canreceive the cell cluster head advertisement updates S to “cooperativeaccess”. The MS that can only receive the adhoc cluster headadvertisement updates the S to “hybrid access”.

If the default access status S of the MS is “direct access”, the cellcluster head advertisement can be received, the distance L between theMS and the BS is greater than the threshold value 2, and the MS updatesthe S to “cooperative access”.

In an embodiment of the present invention, the cluster head tablemaintained by the MS can be as shown in Table 2.

TABLE 2 Cluster Cell Head ID Utilization Rest Energy Path Loss MS 4 U1N_(Restcell4) P_(LossCell4) N_(Rest4) P_(Loss4) MS 5 U1 N_(Restcell5)P_(LossCell5) N_(Rest5) P_(Loss5)  MS 12 U2 N_(Restcell12)P_(LossCell12) N_(Rest12) P_(Loss12) . . . . . . . . . . . .

In Table 2, the P_(LossCell) is a path loss of a link between an MS cellinterface and a cluster head, the N_(RestCell) is energy of the cellinterface, the P_(Loss) is a link path loss between the MS adhocinterface and the cluster head, and the N_(Rest) is energy of the adhocinterface. When the P_(LossCell) is infinite or the N_(RestCell) iszero, it represents that the cell interface is unavailable.

In an embodiment of the present invention, the energy of the cellinterface and the energy of the adhoc interface are managed in a unifiedmode, and at this time N_(RestCell)=N_(Rest).

After finishing update of the access status and the cluster head table,the MS performs confirmation of the cluster head advertisement, and theconfirmation of the cluster head advertisement carries resourceinformation and the access status of the MS. The resource information ofthe MS can include rest energy of the MS and a path loss of the linkbetween the MS and the BS. Specifically, the resource information of theMS can include rest energy of the cell interface of the MS, a path lossof a link between the cell interface and the BS, rest energy of theadhoc interface of the MS, and a path loss of a link between the adhocinterface and the BS.

After receiving the confirmation of the cluster head advertisement fromthe MS, the cluster head updates a virtual cluster table maintained bythe cluster head according to the information carried in theconfirmation of the cluster head advertisement. In an embodiment of thepresent invention, the virtual cluster table maintained by the clusterhead is as shown in Table 3.

TABLE 3 Member Cluster Access BS Path ID Head Mark Status Rest EnergyPath Loss Loss MS 2 No Direct N_(RestCell2) P_(LossCell2) P_(LossBS2)access N_(Rest2) P_(Loss2) MS 3 No Cooperative N_(RestCell3)P_(LossCell3) P_(LossBS3) access N_(Rest3) P_(Loss3) MS 4 ClusterN_(Rest4) P_(Loss4) P_(LossBS4) head in the local zone MS 5 ClusterN_(Rest5) P_(Loss5) P_(LossBS5) head in an adjacent zone

After updating the virtual cluster head table, the cluster head gives acluster-head selection response. The cluster-head selection response cancarry resource information of the cluster head and the information ofthe virtual cluster table maintained by the cluster head. The resourceinformation of the cluster head can include the rest energy of thecluster head and the path loss of the link between the cluster head andthe BS. In order to decrease interferences and facilitate management ofthe BS, in an embodiment of the present invention, only the cellinterface is used for communication between the cluster head and the BS,and at this time the resource information of the cluster head can bespecifically the rest energy of the cell interface of the cluster headand the path loss of the link between the cell interface and the BS.

After receiving the cluster-head selection response from the clusterhead, the BS updates the MS status table according to the informationcarried in the cluster-head selection response. In the embodiment thatonly the cell interface is used for the communication between thecluster head and the BS according to the present invention, the MSstatus table maintained by the BS is as shown in Table 4.

TABLE 4 Member Cluster head list/ ID MS Access Status Rest Energy PathLoss MS 1  Direct access N_(Restcell1) P_(Losscell1) MS 11 Cooperativeaccess (MS 1, P_(Loss11-1)), P_(Losscell11) (MS 13, P_(Loss11-13)) MS 12Hybrid access MS 1, MS 13 MS 13 Direct access N_(Restcell13)P_(Losscell3) . . . . . . . . . . . .

The BS processes the information of the virtual cluster table reportedby the cluster head. For the cluster heads of the same MS, informationof a cluster head list of the MS is formed, so that the BS only needs tosave only information of rest energy of the cluster heads. Based on avirtual cluster head mechanism of clustering zones, cluster heads serveas convergence points of signaling information, so that overhead of theBS is greatly reduced and further reliability can be increased as thesignaling convergence points are not single.

The method for sending packet data according to an embodiment of thepresent invention is illustrated in the following. FIG. 2 shows aprocess of the method for sending packet data according to the firstembodiment. In this embodiment, a processing process of a source MS isillustrated, which includes the following steps.

In step 201, packet data that needs to be sent is obtained.

In step 202, it is determined whether an access status is direct access;if yes, the process turns to step 203; and otherwise, the process turnsto step 204.

Different access modes are used for different access statuses of the MS.In an embodiment of the present invention, default packet-data sendingmechanisms for the MS in different access statuses are as shown in Table5.

TABLE 5 MS status Default Packet-data Sending Mechanism Direct Thepacket data is sent to a BS directly and the BS Access is in charge offorwarding the packet data. A cell interface is used. If a user requiresuse of an adhoc mode, a relay point is selected from a cluster headlist. Cooperative In a cooperative mechanism, a relay point is selectedaccess from the cluster head list for access. A cell interface is used.A cluster head in an adjacent zone may be selected for access. Hybrid Arelay point is selected from a cluster head list access for access. Anadhoc interface is used. A cluster head in an adjacent zone may beselected for access. Adhoc An adhoc interface is used. The mechanism isa conventional adhoc mechanism.

In step 203, the packet data is sent to the BS and the process is ended.

In step 204, a cluster head is selected from the maintained cluster headtable.

Specifically, a source MS can select a cluster head from a cluster headtable according to the following principles.

A. A suitable cell is selected according to the utilization U of a cellin which a cluster head in the cluster head table is located. A clusterhead is selected from the selected cell according to resourceinformation of the cluster head. If utilization U_(local) of the cell inwhich the source MS is located is greater than a threshold value 1 (inan embodiment of the present invention, the threshold value 1 can be90%) and utilization U_(adjacent) of an adjacent cell is smaller than athreshold value 2 (in an embodiment of the present invention, thethreshold value 2 can be 60%), the adjacent cell is selected; andotherwise, the local cell is selected.

B. For cluster heads in the same cell, cluster head selection andinterface selection can be performed according to resource informationof the cluster heads. In an embodiment of the present invention, if therest energy of the cluster head has a large amount and quality of a linkbetween a cluster head and the MS is good, the cluster head is morelikely to be selected. In an embodiment of the present invention, thecluster head is selected through a combined value of rest energy of acluster head and a path loss of a link between the cluster head and theMS. The combined value of the rest energy of the cluster head and thepath loss of the link between the cluster head and the MS can becalculated through the following formula:

arg  min (P_(Loss)^(α)/N_(Rest)), α ≥ 1.

The P_(Loss) is a path loss of a link between an MS adhoc interface anda cluster head, and the N_(Rest) is energy of the adhoc interface.

After the combined value of the rest energy of the cluster head and thepath loss of the link between the cluster head and the MS is calculatedthrough the formula, a cluster head having a larger combined value isselected, so that the cluster head and interface having the optimalcombined value of the rest energy and path loss are selected.Specifically, if the selected cluster head is a cell cluster head, thecorresponding interface is a cell interface. If the selected clusterhead is an adhoc cluster head, the corresponding interface is an adhocinterface.

In an embodiment of the present invention, if the maintained clusterhead table is empty, the source MS can send a relay request to a BS, soas to trigger the BS to perform cluster head selection and clustering,so that the source MS can update a cluster head table according to acluster head advertisement sent by the cluster head, thereby enablingthe source MS to select a cluster head from the updated cluster headtable.

In step 205, the packet data is sent to a cluster head selected from thecluster head table and the process is ended.

As can be seen from foregoing, in this embodiment, the source MS candetermine a mode of sending packet data according to its own accessstatus and a cluster head table is maintained in the MS. When the packetdata is sent, a cluster head only needs to be selected from the clusterhead table and then the packet data is sent to the cluster head ordirectly sent to the BS. As long as information of cluster heads existsin the cluster head table, the MS does not need to send a relay requestto the BS when the packet data is sent, that is, link processing isperformed at the MS, so that resource overhead of the BS is decreasedand at the same time the source MS needs to maintain only theinformation of the cluster heads so that communication complexity can bereduced.

FIG. 3 shows a process of a method for sending packet data according toa second embodiment. In this embodiment, a processing process of asource MS is illustrated, which includes the following steps.

In step 301, packet data that needs to be sent is obtained.

In step 302, it is determined whether an access status is direct access;if yes, the process turns to step 303; and otherwise, the process turnsto step 304.

In step 303, the packet data is sent to the BS and the process is ended.

In step 304, it is determined whether a type of a service correspondingto the packet data is a cell access service; if yes, the process turnsto step 305; and otherwise, the process turns to step 306.

As the source MS has an adhoc and cell interface, the source MS canrealize cell access and adhoc communication inside a virtual cluster atthe same time. The source MS can categorize the services into two majortypes, namely, cell access services and adhoc services, so that twopacket buffers are maintained. For the cell access service, when thecluster head is selected, a cell interface is first selected. For theadhoc service, an adhoc interface is first selected. The services can becategorized according to a use habit of a user, a service distributionsituation at an area in which the source MS is located, andcharacteristics analysis of the services. For a packet having no servicecategory identity, a default packet data sending mechanism is used.

In step 305, a cell cluster head is selected from a cluster head table,the packet data is sent to the cell cluster head, and the process isended.

In step 306, an adhoc cluster head is selected from the cluster headtable, the packet data is sent to the adhoc cluster head, and theprocess is ended.

As can be seen from foregoing, in this embodiment, the source MS candetermine a mode of sending the packet data according to its own accessstatus and a cluster head table is maintained in the MS. When the packetdata is sent, only a cluster head needs to be selected from the clusterhead table and the packet data is sent to the cluster head or directlysent to the BS. As long as information of the cluster head exists in thecluster head table, the MS does not need to send a relay request to theBS when the packet data is sent, that is, link processing is performedat the MS, so that resource overhead of the BS is decreased and at thesame time the source MS needs to maintain only the information of thecluster head, thereby decreasing the communication complexity.Furthermore, the source MS can select an adhoc interface or a cellinterface according to a service type corresponding to the packet datawhen the cluster head is selected, so that the source MS can flexiblyselect an interface for communication.

In the embodiment of the present invention, before the source MS sendsthe packet data to the cluster head, the method further includes addinga Time To Live (TTL) field in the packet data and setting a field valueof the TTL field. Through the set field value of the TTL field, thecluster head can search adjacent cluster heads according to the fieldvalue, so as to increase a success rate of the communication.

FIG. 4 shows a process of a method for sending packet data according toa third embodiment. In this embodiment, a processing process of acluster head is illustrated, which includes the following steps.

In step 401, packet data from a source MS is received. The packet dataincludes an identity of a destination MS.

In step 402, a routing cache table is searched for a path to thedestination MS. If the path to the destination MS is found, the processturns to step 403; if the path to the destination MS is not found, theprocess turns to step 404.

In an embodiment of the present invention, a routing cache tablemaintained by a cluster head is as shown in Table 6.

TABLE 6 Destination MS Next Hop Metric Lifetime MS 11 MS 5  2 10 ms MS12 MS 12 1 10 ms . . . . . . . . . . . .

In step 403, an interface is selected, the packet data is forwardedthrough the selected interface according to the found path, and theprocess is ended.

When the interface is selected, resource information of a cell interfaceof the destination MS and resource information of an adhoc interface ofthe destination MS recorded in a virtual cluster table can be compared.If the resource information of the cell interface is better than theresource information of the adhoc interface, the cell interface isselected; and otherwise, the adhoc interface is selected. Specifically,a combined value of a path loss of a link between the cell interface andthe cluster head of the destination MS and rest energy of the cellinterface of the destination MS can be compared with a combined value ofa path loss of a link between the adhoc interface and the cluster headof the destination MS and rest energy of the adhoc interface of thedestination MS.

In step 404, a virtual cluster head request is sent to a cluster head inan adjacent sector.

The virtual cluster head request includes the identity of thedestination MS, so as to facilitate the cluster head in the adjacentsector to search for the destination MS to check whether the destinationMS is a member of a sector cluster in which the cluster head in theadjacent sector is located.

In step 405, a virtual cluster head response sent by the cluster head inthe adjacent sector is received.

The virtual cluster head response is sent after the cluster head in theadjacent sector finds that the destination MS is the member of thesector cluster.

In step 406, the packet data is sent to the cluster head in the adjacentsector and the process is ended.

Specifically, the packet data can be sent to the cluster head in theadjacent sector through the adhoc interface or the cell interface. In anembodiment of the present invention, in order to decrease interferenceand facilitate management of the BS, only the adhoc interface is usedfor communication between the cluster heads, and at this time the packetdata is sent to the cluster head in the adjacent sector only through theadhoc interface.

If at least two cluster heads in the adjacent sector send the virtualcluster head response, one cluster head in the adjacent sector can befirst selected from the at least two cluster heads in the adjacentsector according to resource information of the cluster heads in theadjacent sector recorded in the virtual cluster table and then thepacket data is sent to the selected cluster head in the adjacent sector.Specifically, one cluster head in the adjacent sector can be selectedfrom the at least two cluster heads in the adjacent sector according tothe resource information of the adjacent cluster head. For example, theselection can be made according to a combined value of rest energy ofthe adjacent cluster head and a path loss of a link between the adjacentcluster head and the interface itself.

As can be seen from foregoing, in this embodiment, when no path to thedestination MS exists in the routing cache table, the cluster head cansend the packet data to a cluster head in the adjacent sector and thepacket data is sent to the destination MS through the cluster head inthe adjacent sector, so that the packet data does not need to be sentthrough the BS, that is, the link processing is performed at the MS,thus decreasing resource overhead of the BS. The cluster head needs tomaintain only information of the cluster head in the adjacent sector andinformation of the MS in the cluster, thus decreasing communicationcomplexity.

FIG. 5 shows a process of a method for sending packet data according toa fourth embodiment. In this embodiment, a processing process of acluster head is illustrated, which includes the following steps.

In step 501, packet data from a source MS is received. The packet dataincludes an identity and a TTL field of a destination MS.

In step 502, a routing cache table is searched for a path to thedestination MS. If the path to the destination MS is found, the processturns to step 503; if the path to the destination MS is not found, theprocess turns to 504.

In step 503, an interface is selected, the packet data is forwardedthrough the selected interface according to the found path, and theprocess is ended.

In step 504, it is determined whether a field value of the TTL field isgreater than 0; if yes, the process turns to step 505; and otherwise,the process turns to step 509.

In step 505, a virtual cluster head request is sent to a cluster head inan adjacent sector.

In step 506, it is determined whether the virtual cluster head responsesent by the cluster head in the adjacent sector is received; if not, theprocess turns to step 507; and otherwise, the process turns to step 508.

In step 507, 1 is subtracted from the field value of the TTL field, andthe process turns to step 504.

In step 508, the packet data is sent to the cluster head in the adjacentsector and the process is ended.

In step 509, the packet data is sent to the BS and the process is ended.

As can be seen from foregoing, in this embodiment, when no path to thedestination MS exists in the routing cache table, the cluster head cansend the packet data to the cluster head in the adjacent sector and thecluster head in the adjacent sector send the packet data to thedestination MS, so that the BS does not need to send the packet data,that is, the link processing is performed at the MS, thus decreasingresource overhead of the BS. The cluster head needs to maintain onlyinformation of the cluster head in the adjacent sector and informationof the MS within the cluster, thus decreasing communication complexity.Furthermore, the cluster head can send a virtual cluster head request tothe cluster heads in the adjacent sector according to the TTL field inthe packet data, so as to expand a communication range and increase asuccess rate of communication.

In an embodiment of the present invention, in order to enable thecluster head to send the subsequent packet data faster, after sendingthe packet data, the cluster head can further update the maintainedrouting cache table according to the sent path.

FIG. 6 shows a process of a method for sending packet data according toa fifth embodiment. In this embodiment, a processing process of a BS isillustrated, which includes the following steps.

In step 601, packet data is received. The packet data includes anidentity of a destination MS.

In step 602, it is determined whether the identity of the destination MScan be found from an MS status table; if not, the process turns to step603; and otherwise, the process turns to step 604.

In step 603, the packet data is sent to a core network and the processis ended.

In step 604, it is determined whether an access status of thedestination MS is direct access; if yes, the process turns to step 605;and otherwise, the process turns to step 606.

In step 605, the packet data is sent to the destination MS and theprocess is ended.

In step 606, a cluster head is selected, the packet data is sent to theselected cluster head, and the process is ended.

Specifically, when the access status of the destination MS is hybridaccess, a cluster head is selected randomly from a cluster head tableand then the packet data is sent to the randomly selected cluster headthrough an adhoc interface.

When the access status of the destination MS is cooperative access, acluster head is selected from the cluster head table according toresource information of the cluster head and then the packet data issent to the selected cluster head through a cell interface.Specifically, a cluster head can be selected from the cluster head tableaccording to a combined value of a path loss of a path between the BSand the cluster head, a path loss of a link between the cluster head andthe MS, and rest energy of the cluster head. In the first embodiment ofthe present invention, the combined value of the path loss of the pathbetween the BS and the cluster head, the path loss of the link betweenthe cluster head and the MS, and the rest energy of the cluster head canbe calculated according to the following expression:arg min(^((P) ^(LossB-C) ^(+P) ^(LossC-M) ⁾ ^(α) /N _(Rest)),α≥1

The P_(LossB-C) is the path loss of the link from the BS to the clusterhead, and the P_(LossC-M) is the path loss of the link from the clusterhead to the MS.

As can be seen from foregoing, in this embodiment, according to theaccess status of the MS, the BS can send the packet data to thedestination MS directly or to the cluster head, so that the cluster headsends the packet data to the destination MS, that is, partial linkprocessing is performed at the MS, thereby decreasing resource overheadof the BS.

An MS according to an embodiment of the present invention is illustratedin the following. FIG. 7 shows a structure of an MS according to a firstembodiment, which includes an obtaining unit 701, a determining unit702, a selecting unit 703, and a sending unit 704.

The obtaining unit 701 is adapted to obtain packet data that needs to besent.

The determining unit 702 is adapted to determine whether an accessstatus of the MS is direct access after the obtaining unit 701 obtainsthe packet data.

The selecting unit 703 is adapted to select a cluster head from acluster head table when the determining unit 702 determines that theaccess status of the MS is not direct access.

The sending unit 704 is adapted to send the packet data to the BS whenthe determining unit 702 determines that the access status of the MS isdirect access, and send the packet data to the cluster head selected bythe selecting unit 703 when the determining unit 702 determines that theaccess status of the MS is not direct access.

As can be seen from the foregoing, in this embodiment, the MS candetermine a mode for sending packet data according to its own accessstatus and a cluster head table is maintained in the MS. When the packetdata is sent, only a cluster head needs to be selected from the clusterhead table and the packet data is sent to the cluster head or sent tothe BS directly. As long as information of cluster heads exists in thecluster head table, the MS does not need to send a relay request to theBS when the packet data is sent, that is, link processing is performedat the MS, so that resource overhead of the BS is decreased, and at thesame time the MS needs to maintain only the information of the clusterheads, so that communication complexity can be decreased.

In an embodiment of the present invention, the determining unit 702 ofthe MS can be further adapted to determine a type of a servicecorresponding to the packet data obtained by the obtaining unit 701 whenit is determined that the access status of the MS is not direct access.At this time, the selecting unit 703 of the MS can be further adapted toselect a cell cluster head from the cluster head table when thedetermining unit 702 determines that the type of the servicecorresponding to the packet data is a cell access service, and select anadhoc cluster head from the cluster head table when the determining unit702 determines that the type of the service corresponding to the packetdata is an adhoc access service. In this embodiment, the MS can selectan adhoc interface or a cell interface according to the type of theservice corresponding to the packet data during selection of the clusterhead, so that the MS can flexibly select an interface for communication.

FIG. 8 shows a structure of an MS according to a second embodiment,which includes a receiving unit 801, an updating unit 802, a sendingunit 803, an obtaining unit 804, a determining unit 805, a selectingunit 806, and a setting unit 807.

The receiving unit 801 is adapted to receive a cluster headadvertisement from a cluster head. The cluster head advertisementincludes resource information of the cluster head and utilization of acell in which the cluster head is located.

The updating unit 802 is adapted to update an access status according tothe cluster head advertisement received by the receiving unit 801 andupdate a cluster head table according to resource information of thecluster head and the utilization of the cell in which the cluster headis located.

The obtaining unit 804 is adapted to obtain packet data that needs to besent.

The determining unit 805 is adapted to determine whether the accessstatus of the MS is direct access after the obtaining unit 804 obtainsthe packet data.

The selecting unit 806 is adapted to select a cluster head from thecluster head table when the determining unit 805 determines that theaccess status of the MS is not direct access.

The setting unit 807 is adapted to add a TTL field in the packet dataand set a field value of the TTL field when the determining unit 805determines that the access status of the MS is not direct access.

By setting the field value of the TTL field, the cluster head can searchan adjacent cluster head according to the field value of the TTL field.

The sending unit 803 is adapted to send cluster head advertisementconfirmation to the cluster head. The cluster head advertisementconfirmation includes resource information of the MS and the accessstatus after update by the updating unit 802, so as to facilitate thecluster head to update the virtual cluster table. When the determiningunit 805 determines that the access status of the MS is direct access,the packet data is sent to the BS. When the determining unit 805determines that the access status of the MS is not direct access, thepacket data in which the TTL field is added by the setting unit 807 issent to the cluster head selected by the selecting unit 806.

As can be seen from the foregoing, in this embodiment, the MS candetermine a mode of sending the packet data according to the accessstatus of the MS itself and a cluster head table is maintained in theMS. When the packet data is sent, only a cluster head needs to beselected from the cluster head table and then the packet data is sent tothe cluster head or sent to the BS directly. As long as information ofcluster heads exists in the cluster head table, the MS does not need tosend a relay request to the BS when the packet data is sent, that is,link processing is performed at the MS, so that resource overhead of theBS is decreased, and at the same time the MS needs to maintain only theinformation of the cluster heads, so that communication complexity canbe decreased. Also, when the MS selects a cluster head, the MS canselect an adhoc interface or a cell interface according to a type of aservice corresponding to the packet data, so that the MS can flexiblyselect an interface for communication. Furthermore, the TTL field isadded in the packet data, so that the cluster head searches an adjacentcluster head according to the field value, so as to expand acommunication range and increase a success rate of the communication.

FIG. 9 shows a structure of an MS according to a third embodiment, whichincludes a receiving unit 901, a searching unit 902, a selecting unit903, and a sending unit 904.

The receiving unit 901 is adapted to receive packet data from a sourceMS. The packet data includes an identity of a destination MS.

The searching unit 902 is adapted to search a path to the destination MSin a routing cache table according to the identity of the destination MSreceived by the receiving unit 901.

The selecting unit 903 is adapted to select an interface when thesearching unit 902 finds the path to the destination MS.

The sending unit 904 is adapted to forward the packet data through theinterface selected by the selecting unit 903 according to the path tothe destination MS found by the searching unit 902.

As can be seen from the foregoing, in this embodiment, when no path tothe destination MS exists in the routing cache table, the MS can sendthe packet data to a cluster head in an adjacent sector, and the clusterhead in the adjacent sector sends the packet data to the destination MS,so that the BS does not need to send the packet data, that is, linkprocessing is performed at the MS, thereby decreasing resource overheadof the BS. In this embodiment, the MS only needs to maintain onlyinformation of the cluster head in the adjacent sector and informationof the MS within the cluster, so that communication complexity can bedecreased.

In an embodiment of the present invention, the sending unit 904 includedin the MS can be further adapted to send a virtual cluster head requestto the cluster head in the adjacent sector when the searching unit 902fails to find the path to the destination MS. The virtual cluster headrequest includes the identity of the destination MS. As the virtualcluster head request includes the identity of the destination MS, thecluster head in the adjacent sector can search for the destination MS tocheck whether the destination MS is a member of a sector cluster inwhich the cluster head of the adjacent sector is located according tothe identity of the destination MS. The receiving unit 901 included inthe MS can be further adapted to receive a virtual cluster head responsesent by the cluster head in the adjacent sector. The virtual clusterhead response is sent after the cluster head in the adjacent sectorfinds that the destination MS is the member of the sector cluster. Thesending unit 904 can be further adapted to send the packet data to thecluster head in the adjacent sector that sends the virtual cluster headresponse. Specifically, the sending unit 904 can include a selectingunit adapted to select one cluster head in an adjacent sector from atleast two cluster heads in the adjacent sector according to resourceinformation of the cluster heads in the adjacent sector recorded in thevirtual cluster table when the receiving unit 901 receives virtualcluster head responses sent by at least two cluster heads in theadjacent sector. A processing unit is adapted to send the packet data tothe cluster head in the adjacent sector selected by the selecting unit.In this embodiment, the MS can select a cluster head in the adjacentsector that has the best resource when a plurality of cluster heads inthe adjacent sector is selectable, so that communication quality isincreased.

FIG. 10 shows a structure of an MS according to a fourth embodiment,which includes a receiving unit 1001, a searching unit 1002, a selectingunit 1003, a calculating unit 1005, a calculation processing unit 1006,a determining unit 1007, an updating unit 1008, and a sending unit 1004.

The receiving unit 1001 is adapted to receive packet data including anidentity of a destination MS from a source MS, receive a virtual clusterhead response sent by a cluster head in an adjacent sector after thecluster head in the adjacent sector finds that the destination MS is amember of the sector cluster, receive a cluster-head selection requestincluding a cell radius, cell utilization, and threshold values of thecluster head from a BS, and receive cluster head advertisementconfirmation sent by the MS which includes resource information of theMS and an access status of the MS after update.

The searching unit 1002 is adapted to search a path to the destinationMS in the routing cache table according to the identity of thedestination MS received by the receiving unit 1001.

The selecting unit 1003 is adapted to select an interface when thesearching unit 1002 finds the path to the destination MS.

Specifically, in an embodiment of the present invention, the selectingunit 1003 can include a comparing unit and a processing unit. Thecomparing unit is adapted to compare resource information of a cellinterface of the destination MS and resource information of an adhocinterface of the destination MS recorded in a virtual cluster table. Theprocessing unit is adapted to select the cell interface when thecomparing unit determines that the resource information of the cellinterface is better than the resource information of the adhocinterface, and select the adhoc interface when the comparing unitdetermines that the resource information of the adhoc interface isbetter than the resource information of the cell interface.

The calculating unit 1005 is adapted to subtract 1 from a field value ofa TTL field when the packet data received by the receiving unit 1001further includes the TTL field and the receiving unit 1001 does notreceive the virtual cluster head response sent by the cluster head inthe adjacent sector, so as to trigger the sending unit 1004 to send thevirtual cluster head request to the cluster head in the adjacent sectoruntil the field value of the TTL field becomes 0.

The calculation processing unit 1006 is adapted to calculate a distancebetween the MS and the BS, and determine whether the MS is located in acluster head zone according to the distance between the MS and the BSand the cell radius received by the receiving unit 1001.

The determining unit 1007 is adapted to determine whether a cluster headthreshold value is satisfied according to the resource information ofthe MS when the calculation processing unit 1006 determines that the MSis located in the cluster head zone.

The updating unit 1008 is adapted to update the access status to directaccess when the determining unit 1007 determines that the resourceinformation of the MS satisfies the cluster head threshold value, andupdate the virtual cluster table according to the resource informationof the MS included in the cluster head advertisement confirmation andthe access status of the MS after update.

The sending unit 1004 is adapted to forward the packet data according tothe path to the destination MS found by the searching unit 1002 throughthe interface selected by the selecting unit 1003, send a virtualcluster head request including the identity of the destination MS to thecluster head in the adjacent sector when the searching unit 1002 failsto find the path of the destination MS to facilitate the cluster head inthe adjacent sector to search for the destination MS to check whetherthe destination MS is a member of a sector cluster in which the clusterhead of the adjacent sector is located, send the packet data to thecluster head in the adjacent sector that sends the virtual cluster headresponse, send a cluster head advertisement when the determining unit1007 determines that the resource information of the MS satisfies thecluster head threshold value to facilitate the MS that receives thecluster head advertisement to update the access status, and send acluster-head selection response including the resource information ofthe cluster head and information of the virtual cluster table to the BSto facilitate the BS to update the MS status table.

As can be seen from the foregoing, in this embodiment, when no path tothe destination MS exists in the routing cache table, the MS can sendthe packet data to the cluster head in the adjacent sector and thecluster head in the adjacent sector sends the packet data to thedestination MS, so that the BS does not need to send the packet data,that is, link processing is performed at the MS, thereby decreasingresource overhead of the BS. In this embodiment, the MS needs tomaintain only information of the cluster head of the adjacent sector andthe information of the MS within the cluster, so that communicationcomplexity can be decreased.

FIG. 11 shows a structure of a BS according to a first embodiment, whichincludes a receiving unit 1101, a searching unit 1102, a determiningunit 1103, a selecting unit 1104, and a sending unit 1105.

The receiving unit 1101 is adapted to receive packet data. The packetdata includes an identity of the destination MS.

The searching unit 1102 is adapted to search the identity of thedestination MS from an MS status table according to the packet datareceived by the receiving unit 1101.

The determining unit 1103 is adapted to determine whether an accessstatus of the destination MS is direct access when the searching unit1102 finds the identity of the destination MS.

The selecting unit 1104 is adapted to select a cluster head when thedetermining unit 1103 determines that the access status of thedestination MS is not direct access.

The sending unit 1105 is adapted to send the packet data to a corenetwork when the searching unit 1102 does not find the identity of thedestination MS, send the packet data to the destination MS when thedetermining unit 1103 determines that the access status of thedestination MS is direct access, and send the packet data to the clusterhead selected by the selecting unit 1104 when the access status of thedestination MS is not direct access.

As can be seen from the foregoing, in this embodiment, the BS can sendthe packet data to the destination MS or the cluster head directlyaccording to the access status of the MS, so as to send the packet datato the destination MS through the cluster head, that is, partial linkprocessing is performed at the MS, so that resource overhead of the BSis decreased.

FIG. 12 shows a structure of a BS according to a second embodiment,which includes a receiving unit 1201, a searching unit 1202, adetermining unit 1203, a selecting unit 1204, a sending unit 1205, andan updating unit 1206.

The receiving unit 1201 is adapted to receive packet data including anidentity of a destination MS and receive a cluster-head selectionresponse for a cluster-head selection request from a cluster head. Thecluster-head selection response includes resource information of thecluster head and information of a virtual cluster table.

The searching unit 1202 is adapted to search the identity of thedestination MS from an MS status table according to the identity of thedestination MS included in the packet data received by the receivingunit 1201.

The determining unit 1203 is adapted to determine whether an accessstatus of the destination MS is direct access when the searching unit1202 finds the identity of the destination MS.

The selecting unit 1204 is adapted to select a cluster head when thedetermining unit 1203 determines that the access status of thedestination MS is not direct access.

The sending unit 1205 is adapted to send the packet data to a corenetwork when the searching unit 1202 does not find the identity of thedestination MS, send the packet data to the destination MS when thedetermining unit 1203 determines that the access status of thedestination MS is direct access, send the packet data to the clusterhead selected by the selecting unit 1204 when the access status of thedestination MS is not direct access, and broadcast a cluster-headselection request. The cluster-head selection request includes a cellradius, cell utilization, and threshold values of the cluster head.

Through the cell radius, the cell utilization, and the threshold valuesof the cluster head included in the cluster-head selection request, theMS that receives the cluster-head selection request can confirm whetherthe MS is the cluster head.

The updating unit 1206 is adapted to update the MS status tableaccording to the cluster-head selection response received by thereceiving unit 1201.

As can be seen from the foregoing, in this embodiment, according to theaccess status of the MS, the BS can send the packet data to thedestination MS directly or to the cluster head so that the cluster headsends the packet data to the destination MS, that is, partial linkprocessing is performed at the MS, so that resource overhead of the BSis decreased, and at the same time the MS status table can be updatedaccording to the cluster-head selection response, so that the records inthe MS status table are kept correct, thereby increasing communicationreliability.

Persons of ordinary skill in the art should understand that all or apart of the steps of the method according to the embodiments may beimplemented by a computer program instructing relevant hardware. Theprogram may be stored in a computer readable storage medium. When theprogram is run, the steps of the method according to the embodiments areperformed. The storage medium may be a magnetic disk, an optical disk, aread-only memory (ROM) or a random access memory (RAM).

The method for sending packet data, the BS, and the MS according to theembodiments of the present invention are illustrated in detail in theforegoing. The description about the embodiments is merely provided forease of understanding of the method and ideas of the present invention.Persons of ordinary skill in the art can make changes to the presentinvention in terms of the specific implementations and applicationscopes according to the ideas of the present invention. Therefore, thespecification shall not be construed as a limit to the presentinvention.

What is claimed is:
 1. A method for sending packet data, comprising:receiving, by a base station (BS), packet data from a mobile station(MS), wherein the packet data comprises an identity of a destination MS;searching, by the BS, the identity of the destination MS in an MS statustable storing respectively information of MSs, access statuses of theMSs to the BS, and information of other MS determined to be a clusterhead for an MS; when the identity of the destination MS is not found inthe MS status table, sending, by the BS, the packet data to a corenetwork; and when the identity of the destination MS is found in the MSstatus table, determining, by the BS, an access status of thedestination MS to the BS in the MS status table, and in response to thedetermining, when the access status of the destination MS to the BS is adirect access status, sending, by the BS, the packet data to thedestination MS, when the access status of the destination MS to the BSis a not direct access status, selecting, by the BS, a cluster head forthe destination MS from the MS status table and sending the packet datato the cluster head, and when the not direct access status of thedestination MS to the BS is cooperative access, the selecting, by theBS, the cluster head comprises selecting, by the BS, the cluster headfrom a cluster head table according to a combined value of a path lossof a path between the BS and the cluster head, a path loss of a linkbetween the cluster head and a MS, and rest energy of the cluster head.2. A method for sending packet data, comprising: receiving, by a basestation (BS), packet data from a mobile station (MS), wherein the packetdata comprises an identity of a destination MS; searching, by the BS,the identity of the destination MS in an MS status table storingrespectively information of MSs, access statuses of the MSs to the BS,and information of other MS determined to be a cluster head for an MS;when the identity of the destination MS is not found in the MS statustable, sending, by the BS, the packet data to a core network; when theidentity of the destination MS is found in the MS status table,determining, by the BS, an access status of the destination MS to the BSin the MS status table, and in response to the determining, when theaccess status of the destination MS to the BS is a direct access status,sending, by the BS, the packet data to the destination MS, and when theaccess status of the destination MS to the BS is a not direct accessstatus, selecting, by the BS, a cluster head for the destination MS fromthe MS status table and sending the packet data to first cluster head;broadcasting, by the BS, a cluster-head selection request within acoverage of a local cell; receiving, by the BS, a cluster-head selectionresponse from a cluster head; and updating, by the BS, the MS statustable according to the cluster-head selection response, wherein thecluster-head selection request carries following parameters: locationinformation of the BS, a cell radius of the local cell, a cellutilization of the local cell, and a cluster-head threshold value.
 3. Abase station (BS), comprising: a memory; a transmitter; a receiver; anda processor, wherein the receiver is configured to receive packet datafrom a mobile station (MS), wherein the packet data comprises anidentity of a destination MS; the processor is configured to, search theidentity of the destination MS in an MS status table stored in thememory, the MS status table to store respectively information of MSs,access statuses of the MSs to the BS, and information of other MSdetermined to be a cluster head for an MS; when the identity of thedestination MS is not found in the MS status table, the transmitter isconfigured to send the packet data to a core network; when the identityof the destination MS is found in the MS status table, perform adetermination of an access status of the destination MS to the BS in theMS status table; and in response to the determination, when the accessstatus of the destination MS to the BS is a direct access status, send,through the transmitter, the packet data to the destination MS, when theaccess status of the destination MS to the BS is a not direct accessstatus, select a cluster head for the destination MS from the MS statustable and send, through the transmitter, the packet data to the clusterhead, and when the not direct access status of the destination MS to theBS is a cooperative access status,  select the cluster head from acluster head table according to a combined value of a path loss of apath between the BS and the cluster head, a path loss of a link betweenthe cluster head and a MS, and rest energy of the cluster head, andsend, through the transmitter, the packet data to the cluster headthrough a cell interface.
 4. A base station (BS), comprising: a memory,a transmitter, a receiver, and a processor, wherein the receiver isconfigured to receive packet data from a mobile station (MS), whereinthe packet data comprises an identity of a destination MS; the processoris configured to, search the identity of the destination MS in an MSstatus table stored in the memory, the MS status table to storerespectively information of MSs, access statuses of the MSs to the BS,and information of other MS determined to be a cluster head for an MS;when the identity of the destination MS is not found in the MS statustable, send, through the transmitter, the packet data to a core network;when the identity of the destination MS is found in the MS status table,perform a determination of an access status of the destination MS to theBS in the MS status table; and in response to the determination, whenthe access status of the destination MS to the BS is a direct accessstatus, send, through the transmitter, the packet data to thedestination MS, and when the access status of the destination MS to theBS is a not direct access status, select a cluster head for thedestination MS from the MS status table and send, through thetransmitter, the packet data to the cluster head; the receiver isfurther configured to receive a cluster-head selection response from acluster head; and the processor is further configured to update the MSstatus table according to the cluster-head selection response, whereinthe cluster-head selection request carries following parameters:location information of the BS, a cell radius of the local cell, a cellutilization of the local cell, and a cluster-head threshold value.